syzbot


INFO: task hung in fuse_simple_request

Status: upstream: reported on 2025/07/15 13:22
Reported-by: syzbot+2a00b97f1a8b18ad3ac3@syzkaller.appspotmail.com
First crash: 10d, last: 10d
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: task hung in fuse_simple_request (2) 1 3 278d 396d 0/3 auto-obsoleted due to no activity on 2025/01/28 01:40
linux-5.15 INFO: task hung in fuse_simple_request 1 12 638d 736d 0/3 auto-obsoleted due to no activity on 2024/02/03 13:59
upstream INFO: task hung in fuse_simple_request fuse 1 C inconclusive error 273 305d 1685d 0/29 upstream: reported C repro on 2020/12/13 21:13
linux-6.1 INFO: task hung in fuse_simple_request 1 6 615d 703d 0/3 auto-obsoleted due to no activity on 2024/02/26 14:29
linux-5.15 INFO: task hung in fuse_simple_request (3) 1 9 33d 146d 0/3 upstream: reported on 2025/03/01 01:36
linux-6.1 INFO: task hung in fuse_simple_request (2) origin:upstream 1 syz 22 17d 399d 0/3 upstream: reported syz repro on 2024/06/21 20:45
upstream INFO: task can't die in request_wait_answer fuse 1 C error 14 1256d 1766d 0/29 auto-obsoleted due to no activity on 2023/04/16 22:02

Sample crash report:
INFO: task syz.0.19525:24646 blocked for more than 143 seconds.
      Not tainted 6.6.98-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.19525     state:D stack:27016 pid:24646 ppid:21891  flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 request_wait_answer fs/fuse/dev.c:407 [inline]
 __fuse_request_send fs/fuse/dev.c:426 [inline]
 fuse_simple_request+0x1195/0x1bb0 fs/fuse/dev.c:513
 fuse_flush+0x5b0/0x830 fs/fuse/file.c:522
 filp_flush fs/open.c:1531 [inline]
 filp_close+0xb1/0x150 fs/open.c:1544
 __range_close fs/file.c:700 [inline]
 __close_range+0x342/0x630 fs/file.c:757
 __do_sys_close_range fs/open.c:1597 [inline]
 __se_sys_close_range fs/open.c:1594 [inline]
 __x64_sys_close_range+0x7a/0x90 fs/open.c:1594
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f297618e929
RSP: 002b:00007ffec6e2e8b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 0000000000210cba RCX: 00007f297618e929
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f29763b7ba0 R08: 0000000000000001 R09: 00000008c6e2ebaf
R10: 00007f2975e00000 R11: 0000000000000246 R12: 00007f29763b608c
R13: 00007f29763b6080 R14: ffffffffffffffff R15: 00007ffec6e2e9d0
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u4:1/12:
1 lock held by khungtaskd/28:
 #0: ffffffff8cd2fae0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8cd2fae0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8cd2fae0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
1 lock held by udevd/5158:
2 locks held by dhcpcd/5453:
2 locks held by getty/5551:
 #0: ffff88814c9f30a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000326e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
2 locks held by kworker/1:16/15477:
 #0: ffff888017872538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #0: ffff888017872538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #1: ffffc9000ba6fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #1: ffffc9000ba6fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted 6.6.98-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x39b/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf41/0xf80 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5453 Comm: dhcpcd Not tainted 6.6.98-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:kernel_text_address+0x34/0xd0 kernel/extable.c:133
Code: ff 00 00 00 81 0f 93 c0 48 81 ff 00 00 a0 8a 0f 92 c1 bd 01 00 00 00 84 c8 75 0c 48 89 fb e8 13 24 a8 ff 85 c0 74 07 89 e8 5b <41> 5e 5d c3 48 c7 c0 00 63 4a 8e 48 c1 e8 03 48 b9 00 00 00 00 00
RSP: 0018:ffffc900037074b8 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffffff81de298e RCX: 0000000000000001
RDX: ffff88802ac65a00 RSI: 0000000000000001 RDI: ffffffff81de298e
RBP: 0000000000000001 R08: ffff88802ac65a00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff8174715c
R13: ffffc90003707920 R14: dffffc0000000000 R15: 1ffff920006e0eaa
FS:  00007efca50d9740(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8c5677f2d8 CR3: 000000002146b000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 __kernel_text_address+0xd/0x30 kernel/extable.c:79
 unwind_get_return_address+0x5d/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1806 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1832
 slab_free mm/slub.c:3816 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3829
 skb_kfree_head net/core/skbuff.c:945 [inline]
 skb_free_head net/core/skbuff.c:957 [inline]
 skb_release_data+0x634/0x800 net/core/skbuff.c:987
 skb_release_all net/core/skbuff.c:1053 [inline]
 __kfree_skb net/core/skbuff.c:1067 [inline]
 consume_skb+0xb2/0x110 net/core/skbuff.c:1283
 __unix_dgram_recvmsg+0xa04/0xd60 net/unix/af_unix.c:2490
 sock_recvmsg_nosec net/socket.c:1046 [inline]
 sock_recvmsg net/socket.c:1068 [inline]
 sock_read_iter+0x2b7/0x3b0 net/socket.c:1138
 call_read_iter include/linux/fs.h:2012 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x431/0x920 fs/read_write.c:470
 ksys_read+0x147/0x250 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7efca5163407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffd8c49bb90 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007efca50d9740 RCX: 00007efca5163407
RDX: 0000000000000408 RSI: 00007ffd8c49bbe0 RDI: 0000000000000007
RBP: 00007ffd8c49c2f0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000055cd01da95e0
R13: 000055cd08bd1df0 R14: 0000000000000000 R15: 00007ffd8c49c0a0
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/15 13:21 linux-6.6.y 9247f4e6573a 03fcfc4b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in fuse_simple_request
* Struck through repros no longer work on HEAD.